About Allergy

According to the American College of Allergy, Asthma, and Immunology, more than 50 million people in the United States are affected by allergies. These reactions range from seasonal allergies to hay fever, asthma, and food allergies.

Allergy testing is widely used to diagnose allergies to specific substances. Information from these tests may help a doctor develop a treatment plan that includes medication, avoidance methods, or immunotherapy (allergy shots).

What Is an Allergy?

Allergies occur when your immune system, the body’s natural defense, reacts to a naturally harmless substance. These substances that cause a reaction are called allergens, which are divided into three primary types:

• Inhaled allergens: This type of allergen affects your body when it comes into contact with the membranes of the nostrils, throat, or lungs. The most common example of an inhaled allergen is pollen.

• Contact allergens: These allergens produce a reaction when they come in contact with your skin. For instance, poison ivy can cause rashes and itching.

• Ingested allergens: This type of allergen is present in certain foods, such as seafood, peanuts, and soy.

An allergic reaction refers to how your body responds to an allergen. A chain of events usually occurs that can lead to allergic reactions.

If you are exposed to a particular allergen that your immune system has identified as harmful even though it’s not, your immune system responds by producing allergic (IgE) antibodies.

The role of allergic antibodies is to locate the allergens and help remove them. As a result, a chemical called histamine is released into your system and causes symptoms of allergies.

What Are the Signs and Symptoms of Allergies?

Allergy symptoms can be classified as mild, moderate, or severe. Mild reactions include local symptoms that only affect a specific area of the body, such as rash, itchiness, runny nose, red and watery eyes, or hay fever.

Moderate reactions include symptoms that spread to other parts of the body. Symptoms may include hives, itchiness, swelling, or trouble breathing.

Some types of allergies can also trigger a severe, life-threatening reaction known as anaphylaxis. The body’s response to the allergen is sudden and affects your whole body.

Anaphylaxis may start with a severe rash and itchiness in your face or eyes. More serious symptoms appear within minutes, including shortness of breath, throat swelling, or vomiting.

Since anaphylaxis causes a drop in blood pressure, it may also cause lightheadedness or even loss of consciousness.

It is best to get an allergy test if you have any of these symptoms. Allergy testing helps identify what you are allergic to.

Types of Allergies

A wide variety of substances can cause an allergic reaction. Depending on the substance involved, its allergy symptoms can affect your skin, airways, nasal passages, sinuses, and digestive system.

Pollen

Seasonal allergic rhinitis, also called hay fever, is an allergic reaction to pollen. This type of nasal allergy usually changes with the seasons due to pollen from plants.

Allergic rhinitis can cause inflammation and swelling of the protective tissue of your eyes (conjunctiva) and the lining of your nose. Symptoms of this allergic disease include:

• Runny nose

• Sneezing

• Congestion (feeling stuffy)

• Itchiness in the nose, eyes, or roof of the mouth

• Red, watery, or swollen eyes (conjunctivitis)

Treatment options for allergic rhinitis include prescription and over-the-counter oral antihistamines, nasal antihistamines, nasal steroids, anti-leukotrienes, and nasal cromolyn.

Exposure to pollen can also cause allergic asthma symptoms, such as wheezing, coughing, shortness of breath, or chest tightness in some people.

Animal Dander

Proteins secreted by sweat glands in an animal’s skin, which are shed in dander, can cause allergic reactions. These reactions may also be caused by the proteins in an animal’s saliva.

Treatment may include medications that control eye, nasal, and chest symptoms. If symptoms are not adequately controlled with medications or avoidance measures, immunotherapy may be recommended.

Dust Mites

Dust mites are tiny organisms that grow in warm, humid areas. They live in dust and the fibers of household objects, such as carpets, mattresses, pillows, and upholstery.

The allergy symptoms from dust mites are similar to those of pollen allergies. Treatment may include medications for eye, nasal, and chest symptoms. Immunotherapy may be recommended if medications and avoidance methods do not work for symptoms.

Insect Sting or Venom

A normal reaction when you get an insect sting includes pain, redness, and swelling around the sting site. You may also experience a large area of local reaction, such as swelling that extends beyond the sting site.

An allergic reaction to an insect sting is the most serious reaction that needs immediate medical attention. Symptoms may include:

• Hives all over the body

• Swelling of the throat, face, or mouth tissue

• Difficulty swallowing or wheezing

• Chest tightness or difficulty breathing

• Rapid pulse

• Dizziness or a sharp drop in the blood pressure

A re-sting can cause a severe, life-threatening reaction. To prevent this, you should get a skin or blood test to confirm your venom allergy. Treatment options include epinephrine (adrenaline) or venom immunotherapy if an allergy is confirmed.

Certain Foods

Some people can develop a specific antibody to a certain food. Allergic reactions occur within minutes of eating the food, and the symptoms can be serious.

The most common food allergies in adults are peanuts, shellfish, and tree nuts. Meanwhile, children may have an allergic reaction to egg, milk, wheat, soy, shellfish, peanuts, and tree nuts.

Food allergies can cause the following symptoms:

• Itching

• Tingling in the mouth

• Hives

• Swelling of the lips, tongue, throat, or face

• Nausea or vomiting

• Diarrhea

• Difficulty breathing

Drug or Medication

A drug allergy is caused by an abnormal reaction of the immune system to a certain medication. Prescription, over-the-counter, or herbal medications are capable of inducing allergic reactions.

Drug allergies are different from a drug’s side effects, which are possible reactions listed on the label. These allergies are also not the same as drug toxicity that is caused by an overdose of medication.

Symptoms of a severe drug allergy often occur within an hour after taking the medication. Other reactions can also occur hours, days, or weeks later. Signs and symptoms include the following:

• Itchy skin

• Rash

• Hives

• Facial swelling

• Fever

• Wheezing

• Shortness of breath

• Anaphylaxis

How Are Allergy Tests Performed?

Allergy testing often involves a skin test or a blood test. You may also need to go on an elimination diet to test for food allergies.

Skin Test

Skin testing is done to determine numerous potential allergens, including airborne, contact, and food-related. There are three types of skin tests: prick, intradermal, and patch tests.

The doctor will usually try a skin prick on the forearm first. A skin prick test, also called a scratch test, checks for immediate allergic reactions to various substances at once.

In this test, the allergen is placed in liquid, then that liquid is placed on a section of the skin. The doctor uses lancets (needles) to lightly puncture the allergen into the skin’s surface.

You will be closely observed to see your skin’s reaction to the foreign substance. If localized symptoms appear over the test site, you are allergic to that specific allergen.

If the skin prick test is inconclusive, the doctor may order an intradermal skin test. This test involves using a needle to inject a tiny amount of allergen into the skin’s dermis layer. Again, the injection site is examined for signs of an allergic reaction.

A patch test is another type of testing that uses adhesive patches containing allergens. These patches are placed on your skin to determine which substance is causing allergic skin inflammation or contact dermatitis.

The patch test can detect delayed allergic reactions, which may take more than 24 hours to develop. After application, the patches will be reviewed before you can get the test results.

Blood Test

Blood testing used to determine an allergic reaction is commonly called ImmunoCAP or radioallergosorbent test (RAST). This test measures the amount of immunoglobulin E (IgE), which are allergy-causing antibodies in the bloodstream.

After getting your blood drawn, the sample is tested in a medical laboratory to show sensitivity to potential allergens.

Elimination Diet

An elimination diet is helpful in diagnosing food allergies, which may be used in conjunction with blood or skin allergy testing. It involves removing certain foods from your diet and adding them back later on. Your reactions will help identify which foods you are intolerant of or sensitive to.